The invention relates generally to electrical networks, and more specifically, to methods of synchronizing input signals into the electrical networks.
Electrical devices may be connected or organized in a network to enable the transmission of power to the devices, or communication between the devices. Such a network of interconnected devices may be described as a grid. For example, an electric grid may be an interconnected network for delivering electricity from one or more power generators to the connected devices (e.g., customers of the utility company). A power grid may transmit AC power at a synchronized frequency, amplitude, and/or phase angle to efficiently connect a large number of power generators and devices. Synchronized operation of a grid, or portions of a grid, may enable a pooling of power generation, as well as a pooling of loads to result in lower operating costs.
The synchronized transmission of AC power may be beneficial for efficiently transmitting and/or distributing of power. However, many factors may disturb the synchronization of a grid. For example, voltage imbalances, angular frequency variations, and voltage harmonic distortions may significantly disturb grid synchronization. In some situations, voltage imbalances may be common in a power grid, as single phase loads of a grid may not be evenly distributed between the phases of the supplied power and may be continuously connected and disconnected. Furthermore, the presence of grid voltage imbalances may generate or propagate voltage harmonic distortions that may have further undesired effects on the synchronization of the grid.
Such discrepancies in the amplitudes, frequencies, and/or phase angles between two parallel voltages may cause abnormal current circulation within the grid, which may result in a large current imbalance. In some power grids, even a small voltage imbalance may result in a large current imbalance. In addition, in some situations, voltage harmonic distortions may disrupt the synchronization of the grid. Imbalanced currents may stress grid devices, such as AC-DC converters, cycloconverters, active filters, induction motors, and other energy storage systems which function to convert and/or transfer power through the grid to the connected electric devices. Imbalanced current may also stress grid link inductors. Accordingly, methods of decreasing the effects of voltage imbalances and/or voltage harmonic distortions may improve the performance and synchronous operation of a grid.